Cellular sets used in wireless communication systems such as cellular networks, personal communication systems and the like typically contain a number of parameters that are programmed when the cellular set is manufactured, a user purchases it and it is activated, or a user changes service providers. For example, programming parameters may include the Mobile Identification Number ("MIN") assigned to the cellular set, or the System Identification Number ("SID") of the wireless system from which the user is obtaining communication services. Within a particular geographic area, cellular sets are typically programmed to operate on one of two frequency bands, generally denominated A or B, each of which has signalling control, voice and paging channels. By regulation designed to foster competition, operators of wireless systems, or carriers, service only a single frequency band in any particular area. Typically, nonwireline carriers are granted the A frequency band while wireline carriers are granted the B frequency band; these assignments are not necessarily permanent, however. Accordingly, the user of the cellular set may have a "home" carrier, from which the user purchased communication services, which operates the A frequency band in the user's home service area, but operates the B frequency band in a second service area. Thus, in different service areas, the same carrier may (and typically does) operate wireless systems on different frequency bands.
A cellular set may be programmed to prefer operation on either the A or B frequency band. Usually the frequency band chosen is the one that the "home" carrier operates in the particular geographic area in which the cellular set was purchased. For instance, if a mobile user purchases a cellular set and associated services from a "home" carrier located in Atlanta, Ga. and operating a wireless system on the B frequency band, the cellular set will be programmed to prefer the B frequency band. If, however, the mobile user travels to Los Angeles, Calif., where the home carrier operates a wireless system on the A frequency band, the cellular set will continue to prefer the B frequency band and the user may not be served by the home carrier. This leads to increased service charges for the user since the operator of the B frequency band in the Los Angeles area may not be associated with the user's home carrier and likely charges higher rates for providing service to a visiting or "roaming" customer. Thus, it is desirable to have the cellular set select whichever frequency band the home carrier of the user may operate in a particular geographic area. Furthermore, if the mobile user of the cellular set roams into an area that its home carrier does not at all service, it is at least desirable to program the cellular set to select a frequency of a foreign carrier with which the home carrier is associated or has negotiated to obtain lower service charges when the mobile user is serviced by the foreign carrier.
These selection functions may be accomplished by providing a cellular set with a list of System Identification Numbers ("SIDs") that identify carriers. The list can be negative (preventing use of listed carriers) or positive (allowing use of listed carriers). Methods for using these lists to select a preferred frequency are disclosed in U.S. Pat. Nos. 4,916,723 to Blair and 5,020,091 to Krolopp, et al. Krolopp, et al. discloses "a process for determining in which system the radio telephone is located and allowing the users to decide whether that number should be used. The process starts with the radio telephone scanning the frequencies assigned to the system in which it is located to find the control channels and determine the system identification code. The received system identification code is then compared with the system identification codes stored in memory in the radio telephone." Through this process, "a radio telephone with multiple set telephone numbers can be used in other cellular systems without requiring the user to memorize or look up which telephone number is used in a particular system." Similarly, Blair discloses a cellular telephone "programmed to scan the available cellular frequencies in search of a home SID carrier signal or alternatively for a carrier signal associated with a SID that is not on an exclusion list, and to indicate the availability of carrier signals on a status display."
Generally, a list or table of SIDs is stored in the memory of a cellular set when it is manufactured and/or activated. During the life of the cellular set, the validity of the foreign wireless systems identified in the cellular set may change, and hence, the list of SIDs corresponding to preferred foreign wireless systems may also need to be changed. Updating or changing the list of SIDs or other programmable parameters within the cellular set is inconvenient, requiring the user to either reprogram the cellular set with the proper parameters herself or (more typically) remove the cellular set and return it to a service center for reprogramming. These options involve substantial labor and inconvenience.
However, a method of updating the data (including the list of SIDs) stored within a cellular mobile radio telephone memory is disclosed in U.S. Pat. Nos. 5,159,625 to Zicker, et al. and 5,046,082 to Zicker, et al. (the "'082 patent"). The '082 patent discloses "a remotely accessible cellular telephone (RACT) which includes operational data stored therein." A method is also disclosed for "detecting the occurrence of an incoming call and answering the incoming call. In another step the call is monitored to detect and identify a signal, and to provide external access to the operational data only if the identifying signal is detected." Another method disclosed in the '082 patent "calls for storing a phone number which corresponds to an administration system and storing a specified call-in time. The method maintains continually updated data which defines a then-current date and time. When the call-in time occurs, the present invention automatically dials the phone number to establish data communication with the data administrative system. A subsequent step then allows the administration system to access the operational data."
While the remote programming method disclosed in the '082 patent is viable, it requires direct communication between the administration system and each RACT. In order to use the method, it is necessary to complete a voice call from the system to the cellular phone and hold the call while reprogramming the phone. As is noted in applicant's U.S. Pat. Nos. 5,526,401 and 5,546,444 both of which are hereby incorporated in their entireties by this reference, this is expensive since the user (or the carrier) must pay for the more expensive voice channel air time used during programming sessions.
Additionally, a wireless system using the method disclosed in the '082 patent must deal with a substantial increase in traffic in the event that reprogramming is necessary on a frequent basis, as is the case in updating lists of SIDs for the cellular sets of numerous customers. Furthermore, the method described in the '082 patent requires that the RP host (computer system) individually contact and update each RACT, a time consuming and burdensome operation that decreases valuable system voice channel capacity. Accordingly, there remains a need for remotely reprogramming or sending data updates (including programming instructions) simultaneously to multiple cellular sets without completing a full call. When the data updates include new SIDs to add to memory, the user of the cellular set can then be assured that it will automatically select the frequency associated with the user's home carrier or an associated carrier. Thus, the user is assured of lower costs because roaming charges are eliminated or reduced, and the carrier's costs decrease as well, since valuable voice channel capacity is conserved.